Lapping machine

ABSTRACT

A lapping machine having superior pressure sensitivity and performance characteristics is driven by a double action hydraulic drive cylinder and controlled by electronic controls and an electro-hydraulic servo valve mechanism. Driving engagement between the drive cylinder and lapping tool is effected by a dual slide arrangement drivingly interconnected by a resilient biasing member, with the drive cylinder being connected to a primary slide and the lapping tool being mounted on a secondary slide. An electronic sensor in the form of an electric eye senses the pressure on the lapping tool and automatically causes the lapping tool to be withdrawn from the work piece when the pressure on the lapping tool reaches a predetermined level. The electronic eye is actuated by relative movement between the slides, and the relative movement is adjustable by varying the tension on the resilient biasing member. The electronic controls are adjustable to permit &#39;&#39;&#39;&#39;lap&#39;&#39;&#39;&#39; and &#39;&#39;&#39;&#39;peck&#39;&#39;&#39;&#39; modes of operation and to provide independent variation of stroke length, up speed, down speed, and the rate of progression of a lapping tool through a work piece. The electronic controls also cause the lapping machine to be turned off automatically when the lapping operation has been completed.

United States Patent [191 Imhoff et al.

[ LAPPING MACHINE [75] Inventors: Harold J. lmhofi, Stuart, Fla.; Jack11. Bennett, Detroit; Dennis E. Turpin, Farmington, both of Mich.

[73] Assignee: Harold J. lmhoff, Stuart, Fla.

[22] Filed: Apr. 11, 1973 [21] Appl. No.: 349,916

Primary Examiner-Harold D. Whitehead Attorney, Agent, or FirmMcGarry &Waters [57] ABSTRACT A lapping machine having superior pressuresensitivitv [451 Sept. 9, 1975 and performance characteristics is drivenby a double action hydraulic drive cylinder and controlled by electroniccontrols and an electro-hydraulic servo valve mechanism. Drivingengagement between the drive cylinder and lapping tool is effected by adual slide arrangement drivingly interconnected by a resilient bias ingmember, with the drive cylinder being connected to a primary slide andthe lapping tool being mounted on a secondary slide. An electronicsensor in the form of an electric eye senses the pressure on the lappingtool and automatically causes the lapping tool to be withdrawn from thework piece when the pressure on the lapping tool reaches a predeterminedlevel. The electronic eye is actuated by relative movement be tween theslides, and the relative movement is adjustable by varying the tensionon the resilient biasing member. The electronic controls are adjustableto permit lap and peck" modes of operation and to provide independentvariation of stroke length, up speed, down speed, and the rate ofprogression of a lapping tool through a work piece. The electroniccontrols also cause the lapping machine to be turned off automaticallywhen the lapping operation has been completed.

19 Claims, 7 Drawing Figures PATENTEDSEP 91975 3.903.653

saw 2 [IF 4 FIG. 3

PATENTEU SEP 9 975 LAPPING MACHINE BACKGROUND OF THE INVENTION 1. Fieldof the Invention This invention relates generally to lapping machinesand more particularly to lapping machines having an electrohydrauliccontrol mechanism and improved pressure sensor.

2. Description of the Prior Art In machine-tool manufacturing, lappingmachines are used primarily for surfacing non-circular internal surfacesin a workpiece where a rotary grinding tool or honing tool cannot beused. In a lapping operation, a lapping tool or lap is supplied with acutting medium such as a liquid slurry containing diamond, Norbide, orother cutting grit and is reciprocated in rubbing engagement with thesurface to be finished to produce a surface cutting action. Thereciprocating lapping tool is progressively fed along the surface untilthe entire surface has been finished.

In lapping a non-circular interior surface of a workpiece, the lappingtool generally is slightly tapered so that as the lapping tool is fedprogressively into the opening, the fit between the lapping tool and thesurface of the workpiece becomes tighter. As the lap cuts away thesurface of the workpiece, the lapping tool is fed progressively into theopening until the entire surface has been finished.

One of the principal problems in lapping operations is that the lappingtool tends to wedge or bind into the cavity if the lapping tool is fedinto the cavity with excessive pressure. To overcome this problem, inearly lapping machines, the forward progress of the lapping tool wascontrolled manually, with an operator regulating the feed by feel. Suchmanual operation, however, was expensive and required many manhours of askilled operator.

In order to avoid the necessity for manual operation of the lappingtool, several attempts have been made to devise lapping machines whichmore or less automatically regulate the inward progress of the lappingtool in response to increases in pressure on the lapping tool. In onesuch type of apparatus, the forward or inward pressure on the lappingtool is provided by a source of resilient pressure (e. g. air pressureor a spring), and the reciprocation of the lapping tool is achieved bymeans of mechanical cam that operates against this forward pressure toreciprocate the lapping tool away from engagement with the work piece.The forward pressure is crudely adjustable so that after the reversemovement of the lapping too caused by the cam, the lapping toolprogresses in a forward direction until the friction between the lappingtool and the work piece overcomes the forward pressure and causes thelapping tool to stop its forward progress. As the lapping tool cuts awaythe surface of the work piece, the stroke of the lapping tool increasesgradually until a switch mechanism sensitive to the length of the strokeof the lapping tool actuates a mechanical drive mechanism that moves thework piece into closer contact with the lapping tool, thus againshortening the stroke of the lapping tool until further cutting actionis achieved.

One of the principal drawbacks of this type of apparatus is that theoperation of the apparatus is dependent upon the wedging of the lappingtool in the work piece upon each reciprocation, and the mechanism bywhich the pressure of the lapping tool into the work piece is regulatedis crude and imprecise. Accordingly, with this type of apparatus, thebinding of the lapping tool in the work piece is a recurrent problem.

Another deficiency with this type of apparatus is that the apparatusrequires a first source of forward pressure and separate drive means forreciprocating the lapping tool and moving the lapping tool progressivelyforward into the internal surface of the work piece. Further, theseparate drive mechanisms for this apparatus are complex and expensive.Accordingly, lapping machines of this design are extremely expensive andnot particularly effective.

Still another drawback with the foregoing lapping machines wherein amechanical cam is employed to produce reverse reciprocation against aforward pressure is that such machines do not permit a wide range ofvariation in lapping conditions. The crude pressure controls of theprior devices permit only limited adjustment of pressure on the lappingtool, and the mechanical cam drive does not permit regulation of thedistance of the reciprocal stroke of the lapping tool. Further, noindependent adjustment of the forward and reverse reciprocation orprogression of the lapping tool are possible. Also, it is not possibleto operate such lapping machines in more than one mode, such as the lapand peck modes described below.

In order to overcome the deficiencies in lapping machines having themechanical cam controls of the apparatus described above, some attemptshave been made to produce lapping machines wherein the reciprocation andthe forward progress of the lapping tool are both controlled by acombination of air and hydraulic drive mechanisms. Such drive mechanismsare preferable to mechanical cam reciprocation mechanisms and are lessexpensive, but, heretofore, they still have encountered problems withlimited control over the pressure on the lapping tool and a lack offlexibility for a wide variety of uses. With these types of lappingmachines, adjustment of pressure on the lapping tool is an inaccurate,time-consuming, and difficult job of manually adjusting air andhydraulic valves. Consequently, even though such apparatus is superiorto a mechanical cam reciprocation apparatus, recurrent problems of toolsbinding in the work pieces are still encountered. Further, heretofore ithas not been feasible to regulate the speed of reciprocation of thelapping tool or the rate at which the lapping tool is fed into the workpiece. In this type of apparatus, the reciprocation speed is about 144rpm, with the rate of progression of the tool into the work piece beingrelatively constant.

In order to overcome the deficiencies in the prior lapping machines, thepresent invention was evolved.

SUMMARY OF THE INVENTION In accordance with the present invention, alapping machine having superior prussure-sensitivity characteristics andperformance characteristics comprises a hydraulic drive means adapted tocontrol the movement of the lapping tool. An electro-hydraulic servovalve mechanism controls the operation of the hydraulic drive, andelectronic controls connected to the electrohydraulic valve control thereciprocation of the lapping tool and the movement of the lapping toolinto and out of the work piece. An electronic sensor generates anelectrical signal whenever the pressure on the lapping tool reaches apredetermined level. Responsive to the electronic signal received fromthe sensor, the electronic controls cause the automatic withdrawl of thelapping tool from the work piece. After the lapping tool has beenwithdrawn from the work piece, the controls cause the lapping tool to bereinserted into the work piece and the cycle repeated.

Improved pressure sensitivity of the present invention is provided byconnecting the hydraulic drive cylinder to a primary or master slide,and mounting the lapping tool on a secondary slide, both of which aremounted for independent linear motion in the same direction in thelapping machine. Resilient baising means in the form of a compressionspring interconnects the two slides so that the forward motion of theprimary slide urges the secondary slide also to move in the firstdirection.

An electronic sensor in the form of an electric eye is responsive torelative movement between the two slides (and, hence, pressure on thelapping tool) and generates an electrical signal triggering thewithdrawal of the lapping tool from the work piece whenever the relativemovement of the two slides in a forward direction reaches apredetermined level. The relative movement of the slides (and pressureon the lapping tool) is adjustable by varying the tension on theresilient biasing means.

The electronic controls of the present invention are adjustable topermit lap and peck modes of operation and to provide independent andwide variation of stroke length, up speed, down speed, and the rate ofprogression of a lapping tool through the work peice. The electroniccontrols also cause the lapping machine to be turned off automaticallywhen the lapping operation has been completed.

Because of the variation and reciprocation speeds available with thelapping machine of the present invention, the machine also may be usedas a filing machine.

These and other advantages and features of the present invention willhereinafter appear and for purposes of illustration, but not oflimitation, a preferred embodiment of the subject of this invention isdescribed in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side plan view of theapparatus of the present invention.

FIG. 2 is a fragmentary front view of the apparatus of the presentinvention, showing the electronic sensor.

FIG. 3 is sectional view taken along lines 33 of FIG. 1.

FIG. 4 is a fragmentary sectional view taken along lines 4-4 of FIG. 2.

FIG. 5 is a block diagram of the hydraulic system of the presentinvention.

FIG. 6 is an electrical wiring diagram showing the power supply andcontrol relay circuitry of the present invention.

FIG. 7 is an electrical wiring diagram showing the electronic controlsof the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings,and more particularly to FIG. 1, a lapping machine 10 embodying theprinciples of the present invention is shown mounted on a table 12, inposition to perform a surfacing function on a workpiece l4. workpiece 14is mounted immediately below the lapping machine on a set-up block orplate 16 which may be raised or lowered by an appropriate liftingmechanism (not shown) in order to move the workpiece into properposition with respect to the lapping tool.

Lapping machine 10 comprises a support bracket 18 which is securelyfastened to the table by means of bolts or other suitable fasteners 20.An adjustable mounting shaft 22 in the form of a horizontally disposedcylinder is mounted in the upper portion of support bracket 18 andextends outwardly therefrom. A vertically disposed frame 24 is mountedon the other end of mounting shaft 22 and extends upwardly therefrom ina line perpendicular to the plane of the table. When the lapping machineis in position for operation, frame 24 is held rigidly in position withrespect to the table.

A vertically disposed wedge-shaped channel 26 is formed in the frontsurface of frame 24 (FIG. 2 orientation), and a master slide 28 isfitted in the channel for slideable motion in a linear direction alongthe frame. For reference purposes, movement of the master slide in adownward direction, according to FIG. 1 orientation, will sometimes bereferred to as movement in a forward" direction and movement in anupward direction will sometimes be referred to as movement in a reversedirection.

A mounting block 30 extends outwardly from the lower portion of masterslide 28 and a wedge-shaped channel 32 is formed in the outer face ofthe mounting block.

A V-block or secondary slide 34 fits within the wedge-shaped channel inthe face of mounting block 30 and is slideable with respect to mountingblock 30 in the same linear direction as the master slide. V-block 34comprises a wedge-shaped base 36 that rides within channel 32 and a toolholding portion 38 that extends outwardly therefrom over work piece 14.Tool holding portion 38 is provided with a flat front surface having aV-shaped indentation therein. A lapping tool 40 comprising a taperedhead 48 and a shank 50 is received in the V-shaped indentation in thetool holding portion, and a mounting plate 42 is fastened securely overlapping tool 40 by means of fasteners 44 and holds the lapping toolsecurely in place. When thus positioned, lapping tool 40 is in verticalaxial alignment with a noncircular opening 46 in work piece 14, suchthat movement of the lapping tool in a forward direction will cause thelapping tool to engage the internal surfaces of opening 46.

Movement of the slides with respect to the frame is achieved by means ofa hydraulic drive cylinder 52, which is mounted on the top of the frameby means of a mounting block 54. Hydraulic drive cylinder 52 comprisesan internally slideable piston 56 and an extendable drive shaft 58, theouter end of which is attached to master slide 28. Hydraulic cylinder 52is a conventional double-action cylinder, wherein the piston is moved ina downward direction by the injection of hydraulic fluid into thecylinder above the piston through an upper inlet conduit 60 and is movedin an upward direction by the injection of hydraulic fluid into thecylinder below the piston through a lower inlet conduit 62, while at thesame time withdrawing hydraulic fluid from upper conduit 60.

Conduits 60 and 62 both lead from hydraulic cylinder 52 to anelectro-hydraulic servo valve 64, which, in

response to appropriate electrical control signals, is adapted toclosely and accurately regulate the operation of hydraulic cylinder 52.The electro-hydraulic servo valve employed in the preferred practice ofthe present invention is commercially available and may be purchasedfrom Hydratech, Pegasus Division, Troy, Mich. 48084. This valvecomprises a movable hydraulic spool valve, which is controlled by a pairof electrically operated solenoids (referred to as up and downsolenoids) mounted in an electrical control element 66 on top of thevalve. These solenoids position the spool valve to cause upward ordownward movement or reciprocation of the piston in the hydrauliccylinder. By appropriate electronic monitoring, this valve is capable ofproducing variable rates of linear reciprocation of piston 56 at speedsof 0 to at least 250 rpm, while at the same time causing the gradualprogression of piston 56 in a forward or reverse direction at any givenrate of speed.

The operation of the servo valve is monitored or controlled byelectrical controls 70, which are connected to the servo valve by meansof an electrical conductor 68.

Hydraulic pressure is provided to the hydraulic cylinder by means of ahydraulic pump 69, shown in block form on the floor underneath thetable. Pump 69 withdraws oil from an oil tank 72 by means of a conduit74 and pumps the oil through another conduit 76 to an inlet in theelectro-hydraulic servo valve. A return conduit 78 leads from the servovalve back to the oil tank 72.

The connection between master slide 28 and secondary slide 34 is bestshown in FIG. 2. A driving plate 80 is attached to the master slide andextends outwardly therefrom at a point above mounting block 30 andsecondary slide 34. Driving plate 80 is provided with a verticallydisposed opening 82 therethrough. A threaded guide rod 84 is mounted onthe top of secondary slide 34 and extends vertically upwardly therefromthrough opening 82 in driving plate 80. A collar 86 threadably engagesguide rod 84, and a resilient biasing means in the form of a compressionspring 88 is interposed between collar 86 and driving plate 80.

Movement of master slide 28 in a forward or reverse direction as aresult of the reciprocation of piston 56 within hydraulic cylinder 52 istranslated to secondary slide 34 in the following manner. As drive plate80 moves downwardly in a forward direction it engages the upper end ofcompression spring 88. As compression spring 88 is compressed, it exertsa corresponding force against the upper side of collar 86. The pressureof spring 88 on collar 86 urges secondary slide 34 to move along withmaster slide 28 in a forward direction and causes lapping tool 40 tomove forwardly into the opening in work piece 14. Since the forceexerted by a spring of this nature is linearly proportional to theamount that the spring is compressed, the force exerted by spring 88 onlapping tool 40 will be proportional to any relative movement of slide28 with respect to the secondary slide 34. Conversely also, relativemovement of the slides will be proportional to the pressure on thelapping tool.

In order to adjust the amount of pressure necessary to trigger thewithdrawal of the lapping tool from the work piece, an electronic sensor90 is incorporated into the drive structure. Sensor 90 comprises anelectronic eye 92 mounted on master slide 28 and a flag 94 mounted onsecondary slide 34. Electronic eye 92 comprises a photocell 96 and alight source 98 which are spaced apart on opposite legs of a U-shapedmounting bracket 100. The space between the legs on mounting bracket 100comprises a vertically oriented slot disposed above flag 94. Electriceye 92 and flag 94 are spaced slightly apart so that when the masterslide and primary slide are not in movement, flag 94 does not interruptthe light beam passing between light source 98 and photocell 96. Afterrelative movement between master slide 28 and secondary slide 34 hasprogressed a predetermined distance, flag 94 interrupts the light beambetween light source 98 and photocell 96. This causes the generation ofan electrical signal, which is received by control mechanism 70 throughline 102. The control mechanism then causes the electrohydraulic servovalve to reverse the direction of piston 56 and hydraulic cylinder 52.As master slide 28 moves in an upward direction a stop plate 103 mountedon the bottom of the master slide engages the secondary slide and raisesthe lapping tool.

In order to adjust the forward pressure required on lapping tool 40before the automatic withdrawal of the lapping tool is effected by theactuation of electric eye 92, it is only necessary to adjust theposition of threaded collar 86 on guide rod 84. If collar 86 is movedupwardly on guide rod 84 so as to precompress the spring beforereciprocation of drive plate 80, a greater amount of pressure will berequired on lapping tool 40 before there will be relative movementbetween slide 28 and secondary slide 34. On the other hand, if collar 88is lowered all the way to the bottom of guide rod 84, a smaller amountof pressure will be required before there is relative movement betweenmaster slide 28 and secondary slide 34. Thus, by controlling position ofcollar 86 on guide rod 84, precise adjustment of the pressure on lappingtool 40 may be achieved.

The structure and details of operation of control mechanism 70 willfirst be explained in connection with the functions that it achieves andthereafter in connection with the electronic circuitry shown in FIGS. 6and 7. Referring to the control panel of the control mechanism shown inFIG. 2, the control mechanism is provided with an on" button 118 and anoff" button 120 of conventional design. The control mechanism is alsoprovided with separate manually adjustable controls to control thelapping tool. These controls include an adjustable up time" control 122and an adjustable down time" control 124, which control the amount oftime that the lapping tool is permitted to move in up and down (orreverse and forward) directions, respectively, before the direction ofmovement is automatically reversed. It is an important feature of thisinvention that, since the drive mechanism of the present invention is adouble-action hydraulic cylinder and not a mere mechanical cam, it ispossible to reciprocate the lapping tool with different forward andreverse speeds. This feature provides advantages for certain types oflapping operations.

Similarly, the control mechanism includes separately adjustable controls126 and 128 for regulating the up speed" and down speed" of the lappingtool, respectively. These controls control the rate at which the lappingtool is moved upwardly and downwardly. The ability to separately controlthe up speed and down speed of the lapping tool is advantageous, becauseit is sometimes desirable to move the reciprocating lapping tool veryslowly in a downward direction into contact will] the work piece,whereas it may be desirable to withdraw the lapping tool rapidly fromthe work piece once the downward cutting cycle has been completed, sothat the cycle may be commenced again as quickly as possible.

Separate controls for both speed and time permit accurate adjustment ofanother characteristic movement of the lapping tool, namely, the strokeof the lapping tool. Since the distance traveled by the lapping tool isa function of both the speed of the tool and the time of movement of thetool is a given direction, the stroke of the tool may be adjusted byvarying either the time or the speed control.

Likewise, the mean position of the lapping tool may be adjusted byvarying the lengths of the upward and downward strokes of the lappingtoo]. By adjusting the speed and/or time controls so that the downwardstroke is longer than the upward stroke, the lapping tool follows agradual move in a downward direction along the workpiece as it follows areciprocating path.

The down times may effectively be disconnected by means of a separatetwo-position switch 130 on the control mechanism in order to operate thelapping machine in either a lap or a peck mode.

When switch 130 is switched to a peck mode, the down timer iseffectively disconnected, so the lapping tool proceeds in a forward ordownward direction until either the electric eye causes automaticwithdrawal of the lapping tool or the lapping tool progresses all theway through the work piece and trips a limit switch 104 which commencesa cycle that automatically turns off the lapping machine.

In the operation of the lapping machine of the present invention in apeck mode, the operator first presses the on button, which starts thedownward movement of master slide 28. The action of drive plate 80 oncompression spring 88 effects a corresponding movement in secondaryslide 34 and lapping tool 40. As lapping tool 40 progresses into theopening in work piece 14, the frictional pressure between the lappingtool and the internal surface of the work piece gradually increases.This frictional pressure resists to a certain extent the movement of thelapping tool into the opening in the work piece. This frictionalresistance is translated to an upward pressure on collar 86 againstcompression spring 88. This force causes the compression of spring 88and the consequent relative movement between master slide 28 andsecondary slide 34. When this relative movement has proceeded to adistance sufficient to permit fiag 94 to interrupt the light beam inelectric eye 92, a control signal is generated which causes thehydraulic drive cylinder to reverse the direction and move master slide28 in a reverse direction. As master slide 28 moves in an upwarddirection, stop plate 103 on the bottom of the master slide engagessecondary slide 34 and pulls it along with the master slide in an upwarddirection. After the upward or reverse movement has proceeded for apredetermined time, which is determined by adjustment of the up timer,the control mechanism automatically causes the drive means to reversedirections and commence moving in a forward direction, so that thelapping tool is moved back into engagement with the internal surface ofthe work piece.

The downward movement of the work piece continues again until thepressure of the lapping tool again exceeds the predetermined cut-offpressure, at which time the lapping tool is again withdrawn from thework piece. This procedure is carried on automatically until the lappingtool removes enough of the material on the internal surface of the workpiece so that the lapping tool may proceed all the way through thesurface to be finished without interruption by electric eye 92.

After the lapping tool has progressed all the way through the opening tobe finished, the lapping machine trips upper limit switch 104 in thefollowing manner. Toggle 105 extends outwardly from limit switch 104 andextends into the path of a projection 108 which is slidably mounted onthe vertical rod 110, which is in turn mounted on the master slide. Theposition of projection 108 on rod 110 may be adjusted by means of anadjustable fastener means (not shown). The position of projection 108 isadjusted so that when the lapping tool is moved all the way through thework piece 14, projection 108 contacts toggle 105, thereby actuatinglimit switch 104. Limit switch 104 then sends an appropriate electricsignal through lead 112 to the control mechanism, which then causes thelapping tool to be withdrawn from the work piece. The master slide movesupwardly until it trips a lower limit switch 106 mounted on the frame atthe lower end of rod 110, which turns the machine off. Limit switch 106is substantially the same as limit switch 104 and comprises a toggle 114that extends into the path of a projection 116 slideably mounted on rod110 below toggle 114. The position of projection 1 16 is adjusted toeffect the disconnection of the lapping machine whenever the drivepiston has raised the master slide to a predetermined point. Lead 1 17connects switch 106 to controls 70.

The operation of the machine in a lap mode is substantially the same asthe peck mode, except that the down timer 122 is placed in operativecondition. Thus, rather than simply proceeding downward until the toolhits resistance or reaches the end of the cycle, the tool proceedsdownwardly until the down timer times out, whereupon the direction ofthe tool is automatically reversed and the up timer is automaticallyactuated. This produces a reciprocating motion, which, as pointd outabove, may be adjusted to cause the gradual downward movement of thetool through the work piece. When the tool has proceeded through theworkpiece, limit switch 104 is tripped and the stop cycle describedabove is repeated.

The electrical circuitry of the present invention is shown in FIGS. 6and 7, with FIG. 6 showing the power supply and relay circuitry and FIG.7 showing the control circuitry. Preferably, the control circuitry ofFIG. 7 and certain diode rectifier circuitry shown in FIG. 6 areemployed in the form of electronic cards.

As shown in FIG. 6, a conventional two-phase volt, 60 ha. alternatingcurrent power source 131 is applied to terminals 132 and 134 and isgrounded at terminal 136. For larger operations, it might of course benecessary to employ 220 three-phase power to provide sufficient powerfor the machine.

Power source 131 is protected by a suitable circuit breaker 138 andpowers the control and drive elements of the circuit through leads 140and 142.

A first branch 144 connected across leads 140 and 142 includes startswitch 118a and a motor control relay R1. Start switch 1180 alsocomprises a second pair of contacts 1 18b in a second branch 146extending across leads 140 and 142. A lead 148 extends between leads 144and 146 at a point between switch 118 and relay R1.

Branch 146 includes in series, in addition to switch 118b, a controlrelay R2, a relay switch R20 (controlled by control relay R2) connectedin parallel with switch 118b; limit switch 104; stop switch 120; relayswitch R2b (controlled by control relay R2) connected in parallel withlimit switch 106; and a relay switch Rla (controlled by motor relay R1).

A third branch 150 connected across leads 140 and 142 comprises a drivemotor 152 and relay switches Rlb and Rlc (both controlled by relay R1).

A fourth branch 154 connected across leads 140 and 142 includestransformer 156 and rectifier 158. Rectifier 158 includes diodes 160 and162 and a center tap ground 164. An output lead 166 connected across theoutputs of diodes 160 and 162 contains a filter 170 in the form of agrounded capacitor. Precise voltage regulation is provided by anintegrated circuit voltage regulator 172, shown in block form.Acceptable units are available commercially from either F airchild orMotorola.

The output B of rectifier 158 appears at terminal 174. Preferably thisvoltage is volts DC. This voltage powers the control elements set forthin FIG. 7.

Starting from the lower left hand corner of FIG. 7, electric eye 92comprises light source 98 connected in parallel with a normallyconductive photocell 96, and powered by power source B. The output ofphotocell 96 is connected by lead 180 to a conventional Schmitt trigger,182, which shapes the wave from the photocell and transforms it to aproper voltage level compatible with the timing mechanism of the presentinvention.

When the flag interrupts the light beam received by photocell 96, thephotocell becomes non-conductive and this causes the Schmitt trigger togenerate a control pulse, which is transmitted to the timing mechanismby lead 184.

The signal transmitted by lead 184 is biased by voltage divider 186 andthen is fed to up time circuit 188, which is a conventional integratedcircuit timer. The up time circuit is controlled by adjustablepotentiometer 190, which is connected in parallel with up time circuit188. The output of up time circuit 188 appears at output terminal 192(corresponding to position 3 in the block diagram of the up time controlcircuit). In operation, the output is high (i.e. 5 volts) when the timeris running and goes to zero volts when the timer has run out.

A lead 193 extends from terminal 192 to a speed control terminal 194 andthen through a capacitor 196 to down time circuit 198, which issubstantially identical to up time control circuit. Down time circuit isadjustable by means of potentiometer 197. This circuit is triggered whenup time control times out and the voltage at terminal 192 drops to zero.

The output voltage of down time circuit appears at terminal 202, whichis connected by lead 204 to lappeck switch 130. When the switch is inits lap position (as shown in FIG. 7) the output signal at terminal 202is conveyed through switch 130 and thereafter by lead 208 to the inputterminal of up time circuit 188. When the output voltage a terminal 202drops to zero this automatically triggers up time circuit 188. Thus,with switch 130 in its lap position, up time circuit 188 and down timecircuit 198 each trigger the actuation of the other when each circuittimes out, which results in a reciprocal action of the separate timecontrol circuits.

When switch is in its peck position, an open circuit exists betweenleads 204 and 208. Accordingly, the output signal of down time circuit198 is not transmitted to the input terminal of up time circuit 188 and,therefore, up time circuit 188 is not triggered when the down timecontrol times out. In either a lap or a peck position, up time circuitis triggered by the actuation of electric eye 92.

The timing controls are connected to the speed controls by means of alead 210 which connects to the timing controls at terminal 194. Thesignal impressed on lead 210 is biased by resistance 212 and thereafterimpressed upon input terminal 214 and 216 of a NAND gate 218. NAND gate218 has an output terminal 220 and functions as follows: if the inputvoltage at both input terminals is high, the voltage at the outputterminal is low. Conversely, if the voltage at either input terminal islow, the voltage at the output terminal is high. Output terminal 220 ofNAND gate 218 is connected to the input terminal 222 of a down speedcontrol NAND gate 224 by means of a lead 226. input terminal 214 of NANDgate 218 is connected by means of a lead 228 to an input terminal 230 ofan up speed control NAND gate 232.

The up and down motion of the lapping tool is controlled by means of anup solenoid 234 and a down solenoid 236 each of which is connected inseries with a conventional two stage amplifier 238 and 240,respectively. Amplifiers 238 and 240 are normally nonconducting and arerendered conducting only when the voltage at the output terminals 246and 245 of NAND gates 232 and 224, respectively, are low (i.e. zerovolts). This occurs only when both input terminals are high.

Output terminals 245 and 246 of NAND gates 224 and 232, are connected bypotentiometers 248 and 250 respectively to power source B and, avariable tap on these potentiometers is connected to input terminals 242and 244 of the respective amplifiers. These potentiometers are thevariable controls for the up and down speed circuits.

Further describing the electric circuitry, the output of NAND gate 224is connected by lead 252 to an input terminal 254 and NAND gate 232.Conversely the output of NAND gate 232 is connected by means of a lead255 to an input terminal 256 of NAND gate 224.

One other circuit control element in this circuit is a wired OR gate257, comprising NAND gate 258, resistance 260 and a relay switch R20(controlled by control relay R2), the operation of which is describedbelow.

The operation of the timer circuitry is as follows: When the up timer isrunning and the output voltage at terminals 192 and 194 is high, thevoltage at both input terminals of NAND gate 218 is high, so the voltageat terminal 220 is low. Thus, the voltage at input terminal 222 of downspeed control NAND gate 224 is low. This makes the voltage at down speedcontrol output terminal high. This makes amplifier 240 staynon-conducting and thereby prevents down solenoid 236 from operating.

At the same time, input terminals 230 and 234 of up speed control NANDgate 232 are both high, so ouput terminal 246 is low. This makesamplifier 238 conduct and renders up speed solenoid operative.

When the up speed timer times out, the voltage at terminals 192 and 194goes low and the opposite voltage signals appear at output terminals 246and 245 of the NAND gates 232 and 224, Thus, amplifier 238 is renderednon-conducting, and amplifier 240 is rendered conducting. Accordingly,up solenoid is deenergized and down solenoid is energized.

With the circuitry being set up in this manner, it is evident thatactuation of the start button will energize only the down solenoid (theup timer not being operative), and when the photocell or the down timeractuates the up timer, the down solenoid is de-energized and the upsolenoid is energized. This cycle repeats itself automatically until themachine operation is terminated.

When the workpiece is finished, wired OR gate 257 overrides the timercircuit and shuts off the machine. When either stop button 120 or limitswitch 104 is tripped, control relay R2 is broken, thereby opening relayswitch R20. This makes the input voltage of NAND gate 258 high and theoutput voltage low. This low voltage is transmitted by line 255 to theoutput terminal 246 of NAND gate 232, thereby energizing the upsolenoid. This same voltage is impressed on input terminal 256 of NANDgate 224 by means of line 262, thereby de-energizing the down solenoid.When the master slide is returned to its original position, limit switch106 is tripped, thereby de-energizing motor relay RI and the hydraulicpump motor.

Additional details of the hydraulic circuitry are shown schematically inFIG. 5. Tank 72 is connected to pump 69 through conduit 74, via filter73. Pump 69 is driven by an electric pump motor 71 through a drive shaft67. Slip oil produced in pump (i.e. oil that slips by the pump) isconducted to a heat exchanger 75 through conduit 77, and the cooled oilis thereafter returned to tank 72 by conduit 79.

Oil pumped by pump 69 is first filtered by filter 81 and then pumped toelectro-hydraulic servo valve 64 through conduit 76. An insolator 83 anda pressure gauge 85 are connected into conduit 76 for purposes ofmeasuring line pressure.

Electro-hydraulic servo valve 64 is provided with inlet conduit 76,outlet conduits 60 and 62, and a return conduit 78, which leads back totank 72. Conduits 60 and 62 iead to hydraulic drive cylinder 52 andcontrol the upward and downward motion of piston 56 and drive shaft 58slidably mounted therein. Up and down solenoids 234 and 236 control theoperation of electrohydraulic servo valve 64.

It should be understood that the embodiments described herein are merelyexemplary of the preferred practice of the present invention and thatvarious changes, modifications, and variations may be made in thearrangements, operations, and details of construction of the elementsdisclosed herein within departing from the spirit and scops of thepresent invention, as set forth in the appended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A lapping machine for finishing a surface in a workpiece by means ofa linearly reciprocating, nonrotating lapping tool comprising:

a frame;

a secondary slide member slidably mounted in the lapping machine forlinear reciprocation movement with respect to the frame in a directiontoward and away from the workpiece, said secondary slide memberincluding means for mounting the lapping tool thereon such thatreciprocation of the secondary slide member brings the lapping tool intoabrading engagement with the surface of the workpiece;

drive means mounted on the frame for reciprocating the secondary slidemember so as to move the lapping tool into and out of abradingengagement with the surface of the workpiece, said drive means beingconnected to the secondary slide member by means of a resilient biasingmeans, said resilient biasing means urging the lapping tool intoengagement with the workpiece in response to movement by the drive meanstoward the workpiece, said resilient biasing means urging the lappingtool against the surface of the workpiece with a pressure that increasesin proportion to the amount of relative movement between the secondaryslide member and the drive means when the drive means is moved towardthe workpiece;

sensor means for sensing the relative movement of the drive means andsecondary slide member in the direction toward the workpiece, saidsensor means generating a control signal when the distance moved by thedrive means exceeds the distance moved by the secondary slide member bya predetermined amount; and

control means for reversing the direction of the drive means so as towithdraw the lapping tool from the workpiece whenever said controlsignal is generated, said control means thereafter causing the drivemeans to commence another reciprocation toward the workpiece.

2. An improvement as claimed in claim 1 wherein the electronic controlmeans comprise manually adjustable speed control means to controlindependently the speed at which the lapping tool is moved in saidforward and reverse directions.

3. An improvement as claimed in claim 1 wherein the electronic controlmeans further comprises manually adjustable up time control means tocontrol independently the amount of time the lapping tool is moved insaid reverse direction before commencement of another reciprocation in aforward direction.

4. An improvement as claimed in claim 3 wherein the electronic controlmeans further comprises manually adjustable down time control means tocontrol independently the amount of time the lapping tool is moved insaid forward direction before movement is reversed to a reversedirection.

5. An improvement as claimed in claim 4 wherein the up time controlmeans is adapted to cause forward movement of the lapping tool and theactuation of the down time control means when the predetermined up timeelapses, and the down time control means is adapted to cause reversemovement of the lapping tool and the actuation of the up time controlmeans when the predetermined down time elapses.

6. An improvement as claimed in claim 5 and further comprising switchmeans for selective disengagement of the down time control means so asto prevent the down time control means from causing reverse movement ofthe lapping tool and actuation of the up time control means when thepredetennined down time elapses.

7. An improvement as claimed in claim 6 and further comprising limitswitch means adapted to override the up and down controls and cause themovement of the lapping tool in a reverse direction out of contact withthe workpiece after the lapping tool has moved a predetermined distancein said forward direction relative to the workpiece, said limit switchmeans being further adapted to turn off the lapping machineautomatically after the lapping tool has moved a predetermined distancein said reverse direction.

8. An improvement as claimed in claim 1 wherein the sensor means isadjustable to adjust the pressure at which the sensor means triggers thewithdrawal of the lapping tool from the workpiece.

9. A lapping machine according to claim 1 wherein the sensor meanscomprises:

photocell means mounted for movement in response to the movement ofeither the drive means or the secondary slide member, said photocellmeans generating said control signal when actuated;

photocell actuating means mounted for movement in response to themovement of the other of the drive means or the secondary slide member,whichever the movement of the photocell means is not responsive to, saidphotocell means actuating the photocell means whenever the forwardmovement of the drive means exceeds the forward movement of thesecondary slide member by said predetermined amount.

10. A lapping machine according to claim 1 wherein:

the photocell means comprises a photocell and light source mounted infixed positions relative to each other, with the light source positionedsuch that it directs light on the photocell when the photocell is notactuated, the control signal from the photocell being produced by theinterruption of the light directed on the photocell by the light source;and

the photocell actuating means is a flag mounted such that the flag movesrelative to the photocell and light source and interrups the lightdirected on the photocell by the light source when the forward movementof the drive means exceeds the forward movement of the secondary slidemember by said predetermined amount.

11. A lapping machine according to claim 10 wherein:

the drive means comprises a hydraulic cylinder mounted on the frame andhaving an extendible drive shaft protruding therefrom;

the control means are electronically operated and includeelectro-hydraulic servo valve means for controlling the operation of thehydraulic cylinder;

a primary slide is mounted for linear motion along the frame and isdrivingly attached to the extendible drive shaft;

the resilient biasing means interconnects the primary and secondaryslides;

the light source and photocell are mounted for movement with the primaryslide; and

the flag is mounted for movement with the secondary slide.

12. A lapping machine as claimed in claim I] wherein the secondary slideis slidably mounted on the primary slide, and the primary slide isslidably mounted on the frame.

13. A lapping machine for surfacing a surface in a workpiece with alapping tool comprising:

a frame;

a primary slide member mounted for slidable movement along a linear pathin forward and reverse directions with respect to the frame;

a secondary slide member mounted for slidable movement along a linearpath in said forward and reverse directions with respect to the frame,said secondary slide member including means for mounting the lappingtool such that the lapping tool will contact the surface of theworkpiece upon movement of the secondary slide member in its forwarddirection;

resilient biasing means interconnecting the primary and secondary slidemembers, said biasing means urging the secondary slide member to travelalong its path in the forward direction in response to the movement ofthe primary slide in the forward direction;

return means for moving the secondary slide member in the reversedirection in response to movement of the primary slide member in thereverse direction;

drive means for moving the primary slide member in either direction onits linear path, said drive means comprising a double-action hydrauliccylinder; and

control means for controlling the operation of the drive means so as toproduce reciprocal motion of the primary slide member and cause aresultant reciprocation of the secondary slide member, said controlmeans comprising:

electro-hydraulic servo valve means for controlling the operation of thehydraulic cylinder in response to electronic controls;

sensor means for causing the drive means to reverse the direction ofmovement of the primary slide from the forward direction to the reversedirection whenever the distance moved by the primary slide in theforward direction exceeds the distance moved by the secondary slide inthe forward dirrection by a predetermined amount, the relative forwardmovement of the primary and secondary slide members through saidpredetermined distance being sensed by photocell means mounted in thelapping machine for movement responsive to the movement of one slide,said photocell means being .actuated to trigger withdrawal of thelapping tool from the workpiece by photocell actuating means mounted formovement in response to the movement of the other slide, said photocellmeans and photocell actuating means being positioned so that thephotocell actuating means actuates the photocell after saidpredetermined relative movement between the slides;

means for causing the drive means to re-reverse the direction of theprimary slide member after predeternined movement of the primary slidemember in the reverse direction; and

electronic control means for controlling independently the forward andreverse speeds of the lapping tool and the amount of time the lappingtool moves in its reverse direction before movement is switched to theforward direction, said control means being manually adjustabe to varyseparately forward speed, reverse speed, and reverse time.

14. A lapping machine as claimed in claim 13 wherein the control meansfurther comprises:

manually adjustable forward time control means for controlling theamount of time the lapping tool is permitted to move in a forwarddirection before the movement is switched to a reverse direction, if themovement is not otherwise reversed by the control means or sensor.

15. A lapping machine as claimed in claim 14 and further comprisinglimit switch means adapted to reverse the movement of the lapping toolto the reverse direction after the lapping tool has proceeded apredetermined distance through the workpiece and thereafter turn off thelapping machine after the lapping tool has been moved for apredetermined distance in the reverse direction.

16. A lapping machine according to claim 13 wherein the primary slide isslidably mounted on the frame for linear movement in said forward andreverse direction and the secondary slide is slidably mounted on theprimary slide for linear movement in said forward and reverse directionswith respect to the frame and the primary slide.

17. A lapping machine according to claim 16 wherein the secondary slideis mounted on the primary slide by means of a dovetail protrusion on thesecondary slide member and a mating dovetail slot in the primary slide,in which the dovetail protrusion rides.

18. A lapping machine according to claim 16 wherein the resiliency ofthe resilient biasing means is adjustable so as to vary the pressurerequired on the lapping tool before the sensor means triggers thewithdrawal of the lapping tool from the workpiece.

19. A lapping machine according to claim 18 wherein the resilientbiasing means is a compression spring interconnecting the primary andsecondary slide members, the resiliency adjustment in said resilientbiasing means comprising adjustment means for varying the length of thespring so as to apply a variable initial compression load on the spring,such adjustment serving to change the lapping tool pressure necessary tocause said predetermined relative movement between the primary andsecondary slide members.

1. A lapping machine for finishing a surface in a workpiece by means ofa linearly reciprocating, non-rotating lapping tool comprising: a frame;a secondary slide member slidably mounted in the lapping machine forlinear reciprocation movement with respect to the frame in a directiontoward and away from the workpiece, said secondary slide memberincluding means for mounting the lapping tool thereon such thatreciprocation of the secondary slide member brings the lapping tool intoabrading engagement with the surface of the workpiece; drive meansmounted on the frame for reciprocating the secondary slide member so asto move the lapping tool into and out of abrading engagement with thesurface of the workpiece, said drive means being connected to thesecondary slide member by means of a resilient biasing means, saidresilient biasing means urging the lapping tool into engagement with theworkpiece in response to moVement by the drive means toward theworkpiece, said resilient biasing means urging the lapping tool againstthe surface of the workpiece with a pressure that increases inproportion to the amount of relative movement between the secondaryslide member and the drive means when the drive means is moved towardthe workpiece; sensor means for sensing the relative movement of thedrive means and secondary slide member in the direction toward theworkpiece, said sensor means generating a control signal when thedistance moved by the drive means exceeds the distance moved by thesecondary slide member by a predetermined amount; and control means forreversing the direction of the drive means so as to withdraw the lappingtool from the workpiece whenever said control signal is generated, saidcontrol means thereafter causing the drive means to commence anotherreciprocation toward the workpiece.
 2. An improvement as claimed inclaim 1 wherein the electronic control means comprise manuallyadjustable speed control means to control independently the speed atwhich the lapping tool is moved in said forward and reverse directions.3. An improvement as claimed in claim 1 wherein the electronic controlmeans further comprises manually adjustable up time control means tocontrol independently the amount of time the lapping tool is moved insaid reverse direction before commencement of another reciprocation in aforward direction.
 4. An improvement as claimed in claim 3 wherein theelectronic control means further comprises manually adjustable down timecontrol means to control independently the amount of time the lappingtool is moved in said forward direction before movement is reversed to areverse direction.
 5. An improvement as claimed in claim 4 wherein theup time control means is adapted to cause forward movement of thelapping tool and the actuation of the down time control means when thepredetermined up time elapses, and the down time control means isadapted to cause reverse movement of the lapping tool and the actuationof the up time control means when the predetermined down time elapses.6. An improvement as claimed in claim 5 and further comprising switchmeans for selective disengagement of the down time control means so asto prevent the down time control means from causing reverse movement ofthe lapping tool and actuation of the up time control means when thepredetermined down time elapses.
 7. An improvement as claimed in claim 6and further comprising limit switch means adapted to override the up anddown controls and cause the movement of the lapping tool in a reversedirection out of contact with the workpiece after the lapping tool hasmoved a predetermined distance in said forward direction relative to theworkpiece, said limit switch means being further adapted to turn off thelapping machine automatically after the lapping tool has moved apredetermined distance in said reverse direction.
 8. An improvement asclaimed in claim 1 wherein the sensor means is adjustable to adjust thepressure at which the sensor means triggers the withdrawal of thelapping tool from the workpiece.
 9. A lapping machine according to claim1 wherein the sensor means comprises: photocell means mounted formovement in response to the movement of either the drive means or thesecondary slide member, said photocell means generating said controlsignal when actuated; photocell actuating means mounted for movement inresponse to the movement of the other of the drive means or thesecondary slide member, whichever the movement of the photocell means isnot responsive to, said photocell means actuating the photocell meanswhenever the forward movement of the drive means exceeds the forwardmovement of the secondary slide member by said predetermined amount. 10.A lapping machine according to claim 1 wherein: the photocell meanscomprises a photocell and light source mounted in fixed positionsrelative to each other, with the light sourCe positioned such that itdirects light on the photocell when the photocell is not actuated, thecontrol signal from the photocell being produced by the interruption ofthe light directed on the photocell by the light source; and thephotocell actuating means is a flag mounted such that the flag movesrelative to the photocell and light source and interrups the lightdirected on the photocell by the light source when the forward movementof the drive means exceeds the forward movement of the secondary slidemember by said predetermined amount.
 11. A lapping machine according toclaim 10 wherein: the drive means comprises a hydraulic cylinder mountedon the frame and having an extendible drive shaft protruding therefrom;the control means are electronically operated and includeelectro-hydraulic servo valve means for controlling the operation of thehydraulic cylinder; a primary slide is mounted for linear motion alongthe frame and is drivingly attached to the extendible drive shaft; theresilient biasing means interconnects the primary and secondary slides;the light source and photocell are mounted for movement with the primaryslide; and the flag is mounted for movement with the secondary slide.12. A lapping machine as claimed in claim 11 wherein the secondary slideis slidably mounted on the primary slide, and the primary slide isslidably mounted on the frame.
 13. A lapping machine for surfacing asurface in a workpiece with a lapping tool comprising: a frame; aprimary slide member mounted for slidable movement along a linear pathin forward and reverse directions with respect to the frame; a secondaryslide member mounted for slidable movement along a linear path in saidforward and reverse directions with respect to the frame, said secondaryslide member including means for mounting the lapping tool such that thelapping tool will contact the surface of the workpiece upon movement ofthe secondary slide member in its forward direction; resilient biasingmeans interconnecting the primary and secondary slide members, saidbiasing means urging the secondary slide member to travel along its pathin the forward direction in response to the movement of the primaryslide in the forward direction; return means for moving the secondaryslide member in the reverse direction in response to movement of theprimary slide member in the reverse direction; drive means for movingthe primary slide member in either direction on its linear path, saiddrive means comprising a double-action hydraulic cylinder; and controlmeans for controlling the operation of the drive means so as to producereciprocal motion of the primary slide member and cause a resultantreciprocation of the secondary slide member, said control meanscomprising: electro-hydraulic servo valve means for controlling theoperation of the hydraulic cylinder in response to electronic controls;sensor means for causing the drive means to reverse the direction ofmovement of the primary slide from the forward direction to the reversedirection whenever the distance moved by the primary slide in theforward direction exceeds the distance moved by the secondary slide inthe forward dirrection by a predetermined amount, the relative forwardmovement of the primary and secondary slide members through saidpredetermined distance being sensed by photocell means mounted in thelapping machine for movement responsive to the movement of one slide,said photocell means being actuated to trigger withdrawal of the lappingtool from the workpiece by photocell actuating means mounted formovement in response to the movement of the other slide, said photocellmeans and photocell actuating means being positioned so that thephotocell actuating means actuates the photocell after saidpredetermined relative movement between the slides; means for causingthe drive means to re-reverse the direction of the primary slide memberafter predeternined movEment of the primary slide member in the reversedirection; and electronic control means for controlling independentlythe forward and reverse speeds of the lapping tool and the amount oftime the lapping tool moves in its reverse direction before movement isswitched to the forward direction, said control means being manuallyadjustabe to vary separately forward speed, reverse speed, and reversetime.
 14. A lapping machine as claimed in claim 13 wherein the controlmeans further comprises: manually adjustable forward time control meansfor controlling the amount of time the lapping tool is permitted to movein a forward direction before the movement is switched to a reversedirection, if the movement is not otherwise reversed by the controlmeans or sensor.
 15. A lapping machine as claimed in claim 14 andfurther comprising limit switch means adapted to reverse the movement ofthe lapping tool to the reverse direction after the lapping tool hasproceeded a predetermined distance through the workpiece and thereafterturn off the lapping machine after the lapping tool has been moved for apredetermined distance in the reverse direction.
 16. A lapping machineaccording to claim 13 wherein the primary slide is slidably mounted onthe frame for linear movement in said forward and reverse direction andthe secondary slide is slidably mounted on the primary slide for linearmovement in said forward and reverse directions with respect to theframe and the primary slide.
 17. A lapping machine according to claim 16wherein the secondary slide is mounted on the primary slide by means ofa dovetail protrusion on the secondary slide member and a matingdovetail slot in the primary slide, in which the dovetail protrusionrides.
 18. A lapping machine according to claim 16 wherein theresiliency of the resilient biasing means is adjustable so as to varythe pressure required on the lapping tool before the sensor meanstriggers the withdrawal of the lapping tool from the workpiece.
 19. Alapping machine according to claim 18 wherein the resilient biasingmeans is a compression spring interconnecting the primary and secondaryslide members, the resiliency adjustment in said resilient biasing meanscomprising adjustment means for varying the length of the spring so asto apply a variable initial compression load on the spring, suchadjustment serving to change the lapping tool pressure necessary tocause said predetermined relative movement between the primary andsecondary slide members.